Hot melt adhesives have been used to bond a variety of materials to many substrates. James P. Szymanski et al., U.S. Pat. No. 5,204,390, discloses pressure-sensitive hot melt adhesives comprising substantially saturated block copolymers, tackifying resin, and polybutene. This hot melt composition exhibits adhesive stability when exposed to ultra-violet light and is stable when contacted with plasticized surfaces.
Removable or releasable hot melt pressure-sensitive adhesives (PSA's) for articles such as feminine napkins, adult incontinent pads and the like are described as "garment attachment" or "positioning" adhesives. During manufacture of such articles, the hot melt PSA is typically slot-coated directly or transfer coated onto a polyolefin film substrate and then covered with a release liner. There are a multitude of patents pertaining to adhesive compositions for tapes, labels, adhesive bandages and the like. Collins et al., U.S. Pat. No. 4,136,699 specifically relates to hot melt PSA positioning adhesive compositions comprising substantially saturated block copolymers for feminine napkins.
In recent years, manufacturers have attempted to replace the continuous slot-coat method with various discontinuous methods, particularly by spray application methods, such as spiral spray and melt blown techniques or by pattern coating methods, otherwise referred to as screen-printing. There are several advantages in using a pattern coating technique, including aesthetic advantages due to the variety of screen designs as well as the ability to strategically place adhesive in precise locations. The primary advantage pattern coating offered is the ability to vastly reduce adhesive consumption, since the surface area per mass of adhesive is greatly increased.
However, hot melt PSAs employed for slot-coat applications tend to exhibit hot melt adhesive transfer to the surface it is removed from when coated discontinuously onto a substrate. Further, the hot melt adhesives known from the prior art have the drawback that they cause skin irritation when in contact with skin for a period of time. To counteract such skin irriation, the adhesive compositions of the prior art necessitate the addition of zinc oxide. Moreover, articles constructed from these hot melt adhesives often do not adhere properly to skin and thus can easily shift and become unattached. Finally, the hot melt adhesive compositions known from the prior art can separate from the substrate permanently adhered to due to mechanical influence.
Hence, industry would find advantage in a hot melt adhesive composition wherein the adhesive is permanently adhered to a substrate and is removably attachable to skin in order to secure an article for a period of time and can be subsequently removed without causing skin irritation or adhesive transfer.